Jet Flow Nozzle Protrusions for Noise Reduction Without Thrust Loss
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Solution Overview
Problem
Current jet flow nozzles either fail to adequately reduce noise due to the complexity and thrust loss associated with micro jet nozzle configurations, or they introduce new high-frequency noise sources, while existing jet flow nozzles with mixers are insufficient in noise reduction and cause thrust loss by slowing down the jet flow.
Innovation Solution
A jet flow nozzle design featuring protrusions and grooves around the nozzle outlet end that gently bend the mixed layer of jet and external air flows, reducing velocity gradients and shear forces, thereby suppressing vortex growth and noise emission without the need for air bleeding or slowing down the jet flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a mixer is used to block the jet flow path, then noise reduction is promoted by facilitating mixing of jet flow and external air flow, but thrust loss occurs due to slowing down of the jet flow
Solution Approach 1:
The nozzle outlet end is divided into multiple circumferential regions with different protrusion heights, creating segmented zones that progressively bend the mixed layer. This segmentation allows different parts of the jet flow to be treated differently, achieving noise reduction through controlled bending while maintaining overall flow momentum and avoiding thrust loss.
Solution Approach 2:
Different circumferential regions of the nozzle outlet end are assigned different protrusion heights (first, second, and third heights), creating local variations in flow bending intensity. This local quality approach allows the mixed layer to be bent more aggressively in certain regions while maintaining gentler bending in others, optimizing both noise reduction and thrust preservation.
2Object-affected harmful factors
If micro jet nozzles are used to inject air flow toward the core flow, then noise reduction is achieved by bending the mixed layer, but device complexity increases due to the need for air bleeding systems
Solution Approach 1:
The protrusions on the nozzle outlet end utilize the existing jet flow and external air flow to bend the mixed layer naturally, without requiring additional air bleeding systems or external power sources. The structure serves itself by using the flow dynamics already present in the system, achieving noise reduction while avoiding the complexity of micro jet nozzle systems.
Solution Approach 2:
The protrusions act as an intermediary structure between the jet flow and external air flow, mediating their interaction by bending the mixed layer. This intermediary approach achieves the noise reduction effect of micro jet nozzles through a simpler geometric feature rather than requiring complex active injection systems.
3Object-affected harmful factors
If protrusions with varying heights are used to bend the mixed layer, then noise reduction is achieved by reducing velocity gradients, but manufacturing precision requirements increase
Solution Approach 1:
The protrusions are segmented into three distinct height levels (first, second, and third heights) distributed across different circumferential regions. This segmentation into discrete levels simplifies manufacturing compared to continuous height variations, as each level can be produced using standard machining operations while still achieving the desired flow bending effect.
Solution Approach 2:
The asymmetric distribution of protrusion heights around the circumferential direction creates intentional flow bending patterns that optimize noise reduction. The asymmetric design is achieved through conventional machining by positioning protrusions at specific angular intervals with different heights, avoiding the need for highly precise symmetric patterns while maintaining effectiveness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design achieves noise reduction comparable to micro jet nozzles in the low-frequency range and superior to traditional jet flow nozzles in both low- and high-frequency noise, while maintaining a simpler configuration and avoiding thrust loss, by effectively bending the mixed layer and reducing turbulent kinetic energy.
Implementation Method 1
the mixed layer of the jet flow and the external air flow is bent by the protrusions
Implementation Method 2
the velocity gradient of the fluid in the mixed layer becomes gentle, and thus it is possible to prevent an increase in velocity gradient. For this reason, as in the law of the noise reduction using the micro jet nozzle, by bending the mixed layer of the jet flow and the external air flow, a reduction of shear force in the mixed layer is promoted
Implementation Method 3
the growth of a vortex formed near the nozzle outlet end is suppressed, and as a result, it is possible to suppress the occurrence of a large vortex serving as the main cause of noise
Implementation Method 4
maximum turbulent kinetic energy in the mixed layer near the nozzle outlet end is reduced, and thus, it is possible to reduce high-frequency noise
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
The present invention relates to a jet engine including protrusions (1) for preventing the increase of the velocity gradient of a fluid in a mixed layer of a jet flow and an external air flow by bending the mixed layer, when viewed from the side of a jet flow injected.